Multi-beam satellite communications system

ABSTRACT

A satellite communications system having ground user terminals, hubs, and a geosynchronous satellite. The satellite generates a network of spot beam coverage areas on the earth. A hub and at least one ground terminal are located in each of at least two spot beams. A first user terminal transmits an uplink signal according to a first signal protocol to the hub through the satellite. A second user terminal receives a downlink signal according to a second signal protocol through the downlink spot beam from the hub through the satellite. The hub may be located in the same spot beam coverage area as the first or the second user terminal or may be located in an altogether different spot beam coverage area. Through selective frequency and/or polarization routing on board the satellite, a hub located within a “parent” beam can communicate with user terminals within the parent beam at a specified frequency and polarization, and can communicate with users in other “dependent” beams on a different frequency and/or polarization. This routing allocates the total available bandwidth between parent and dependent beams. The system enables asynchronous communications between each hub and the satellite to maximize frequency re-use and the overall capacity of the system.

RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional PatentApplication Serial No. 60/156,170 filed on Sep. 27, 1999.

TECHNICAL FIELD

[0002] This invention relates to satellite communications systems usingmultiple spot beams from a geosynchronous earth orbit satellite toprovide selective coverage of the continental United States and, moreparticularly, relates to a system having a satellite receiving hub inevery spot beam that allows for asynchronous communications between eachhub and the satellite for maximizing frequency re-use.

BACKGROUND OF THE INVENTION

[0003] The rapid growth of the Internet and the unavailability ofhigh-speed connections from standard telephone lines and local cableproviders have resulted in an intense search for an alternativehigh-speed mode of communications. Satellite communications (“SATCOM”)systems are a natural selection for replacing conventional land-basedcommunications systems as a means of providing high-speed digitalcommunications new links.

[0004] Typical SATCOM system configurations are shown in FIGS. 1-3. FIG.1 is an illustration of a SATCOM “bent-pipe” configuration for twoground terminals located within the same beam. In the bent-pipeconfiguration, a first ground terminal 102 transmits a signal on theuplink frequency band to a GEO satellite 108. Upon reception of thesignal, the GEO satellite shifts the frequency of the signal to adownlink frequency and retransmits the signal to the second groundterminal 104. The “bent-pipe” configuration does not require thesatellite to have on-board processing. Rather, the satellite merely actsas a relay from one ground terminal to another ground terminal. Becausethe satellite does not have on-board processing, the “bent-pipe”configuration is typically limited to use within a single beam 106.

[0005] Another standard SATCOM configuration is shown in FIG. 2, whichillustrates a SATCOM “hub” configuration. In the “hub” configuration, aseries of ground terminals 202, 204 and a single hub 206 are locatedwithin a single beam 208. The hub acts as a two-step bent-pipeconfiguration, in which the uplink signal is routed from the GEOsatellite 210 to an intermediate ground hub 206. The hub acts as a localcontrol center to assign channels and other functions associated withthe network management. The intermediate stop typically adds anadditional ¼-second to the signal propagation delay normally associatedwith the round-trip to a GEO satellite, which is unacceptable forhigh-quality telephony services. In order to avoid this additionaldelay, the hub configuration can also operate as a “bent-pipe”configuration, in which the hub is bypassed and the downlink signal isrouted directly to a second ground terminal.

[0006] Additionally, ground terminals within the hub configuration mayalso operate in a one-way “broadcast” mode, in which a single groundterminal transmits an uplink signal to the GEO satellite, which shiftsthe frequency for transmission on the downlink channel. However, insteadof simply transmitting the downlink signal to a single ground terminal,the satellite “broadcasts” the signal over the downlink channel to everyground terminal within the beam.

[0007] Still another standard SATCOM configuration is shown in FIG. 3,which is an illustration of the SES ARCS SATCOM system. The ARCS SATCOMsystem combines DVB technology on the downlink signal with a high-speedsatellite uplink signal. The ARCS SATCOM system uses a standard Ku-BandDVB downlink 314 and a “piggyback” Ka-band payload, which routes Ka-banduplinks 316 from individual ground terminals 304 to a single hub 306,located in Luxembourg. The ARCS SATCOM system provides eight beams 302on the Ka-band uplink, each of which has a footprint of approximately500 miles diameter on the earth. As a result of this high gain from thereceive antenna on the satellite 308, a dish only 75 cm in diameter witha ½ W transmitter can provide 144 Kbps return channel data rate. TheKa-band uplinks from all eight of the beams are returned to the singlehub in Luxembourg for processing. The DVB video data for the Ku band isbroadcast on an uplink signal 312 to the satellite from the hub 306, andis re-broadcast on the downlink signal using Ku-band DVB transponders.

[0008] Conventional SATCOM systems using geosynchronous earth orbits(“GEO”) satellites have typically provided two types of services: (a) arelay mode, in which the GEO satellite merely relays a signal from oneearth terminal to another, and (b) a broadcast mode, in which the GEOsatellite transmits a signal to a large number of ground terminals. Inthe relay mode, also known as a “bent-pipe” mode, a ground terminaltransmits a signal using an uplink frequency to the GEO satellite, whichretransmits the signal to a second ground terminal using a downlinkfrequency. This mode is illustrated in FIG. 1. Because the transmissionfootprint of the GEO satellite on the earth surface is large, the powerdensity of the signal is very low. This requires that the receivingantenna be sufficiently large, ranging from one to three meters indiameter, to achieve the requisite antenna gain. However, these largeantennas are practical only for large, commercial users. Individualconsumers cannot afford the space or expense of these large groundantennas. Individual consumers are willing to tolerate only smallantennas, such as those used for direct broadcast satellite (DBS)transmissions, which are typically one to two feet in diameter.

[0009] Small ground antennas often operate with a “hub” service, inwhich the user uplink is routed from the satellite to an intermediateground station known as the. “hub.” This service is illustrated in FIG.2. The hub usually acts a local control center to assign channels andother functions associated with network management. This intermediate“stop” adds an additional ¼ second to the propagation delay associatedwith the round trip to synchronous orbit, so the total delay in oneterminal transmitting to another is approximately ½ second—a delay manyconsider too long for viable high quality telephony today. The GEOsatellite can also operate in a “mesh” configuration in which the userdownlink is routed directly to the other user without the hubtransmission.

[0010] In the broadcast mode, a hub or “feeder link” sends the entirespectrum of broadcast signals to the GEO satellite, which thenrebroadcasts the signals to the region of interest. It is important tonote that in the broadcast service all users receive the same signals,which are typically transmitted at nearly equal power levels because theground terminals are assumed to receive the entire band of signalseverywhere. The broadcast spectrum is divided up into a number oftransponder bandwidths, each of which can carry a multiple of standardTV channels, high definition TV, or data. This type of transmission hasbecome especially important in the direct broadcast satellite (“DBS”) ofstandard broadcast television as a competing service to cable.

[0011] Typically, GEO SATCOM systems use a single wide area coveragebeam with a diameter of approximately 2,500 miles to provide completecoverage of CONUS. Therefore, in order for a ground antenna to receiveadequate signal strength, the transmitter on the satellite must havesufficient power to provide an adequate power density within the singlewide area coverage beam. However, this greatly increases the cost andcomplexity of the GEO satellite.

[0012] Another way to ensure that the ground terminal receives adequatesignal strength is to use a ground station with a large diameter antennato achieve the requisite gain. However, as the size of the antennaincreases, so does the expense. Therefore, only commercial users areable to afford these antennas. Clearly, this solution is unacceptable toindividual users, who demand cheaper, more aesthetically pleasing,smaller antennas.

[0013] Several attempts have been made to address this problem. Onesolution is to use a number of smaller spot beams instead of a singlewide area coverage beam to cover the same geographical area. Bydecreasing the size of the spot beams while maintaining the same overalltransmitted power, the power density within each spot beam increases.The increase in the power density within each spot beam enables the useof smaller ground antennas.

[0014] However, conventional systems employing spot beams typically onlyemploy a single hub for the entire system. For example, in Europe, SESis preparing to deploy the ARCS system using the Astra 11H and 1Ksatellites to provide multi-beam coverage of Europe. The Astra 1H uses astandard Ku-Band direct video broadcast (“DVB”) downlink and a“piggyback” Ka-band payload which routes individual user Ka-band uplinksto a single, central hub located in Luxembourg. The ARCS system useseight beams on the Ka-band uplink, with each beam having a footprint ofapproximately 500 miles diameter on the earth to provide completecoverage of Europe. As a result of this high gain from the satellitereceive antenna, a ground antenna of only 75 cm diameter with a ½ Wtransmitter can provide a 144 Kbps return channel data rate. The Ka-banduplinks from all eight of the beams are returned to the single hub inLuxembourg. The Ku-band data for the DVB is broadcast up from a feederlink to the satellite from the Luxembourg hub and is broadcast down tothe area covered by all eight spot beams through a single broadcast beamwith Ku-band DVB transponders. A single-hub ARCS system employing spotbeams is illustrated schematically in FIG. 3.

[0015] Other satellite systems being planned now propose to provide abent-pipe mode between individual ground terminals in different spotbeams. These satellites plan to use digital processing on board in orderto route the signal from one spot beam to another, which greatlyincreases the cost of the system.

[0016] Thus, there is a general need in the art for a SATCOM systemusing multiple spot beams to cover at least selected areas of the CONUS.There is a further need in the art for a SATCOM system which has a hubin every spot beam.

SUMMARY OF THE INVENTION

[0017] The present invention meets the above-described need by providinga SATCOM system having ground terminals, hubs, and at least onesatellite stationed in a geosynchronous earth orbit (GEO) about theearth. The GEO satellite generates a network of spot beams coveringselected area(s). A single hub and at least one ground terminal residewithin each spot beam. A user terminal with a well-defined protocol cantransmit an uplink signal to the hub through the GEO satellite. The userterminal also can receive a signal having a second well-defined protocolthrough the downlink spot beam from the hub through the GEO satellite.For example, the uplink from the ground terminal might use a MF/TDMAmultiple access method to maximize the number of users who can be“on-line” at given time. The corresponding downlink signal might may usethe standard “DVB-S” protocol, which supports both video and datatransmissions.

[0018] The invention may also support a mode of operation where severalindividual spot beams shall share a single hub in a “parent/dependent”operational mode. Through selective frequency and/or polarizationrouting on board the satellite, a hub located within a “parent” beamwould communicate with user terminals within the parent beam at aspecified frequency and polarization and would communicate with users inother “dependent” beams on a different frequency and/or polarization.This routing would divide the total available bandwidth between theseparent and dependent beams. Routing on board the satellite could beimplemented to allow eventual separation between the parent anddependent beam by inclusion of a switch built into the on-board routing.This would allow full use of the available bandwidth in each beam. Thismethod of deployment could allow a more gradual installation of hubs torestrict ground equipment costs at the beginning of service provision.

[0019] The invention may also support a second class of service, inwhich the hub downlink uses a second protocol that is adopted fortransmission from a “commercial” ground terminal. The commercial groundterminal may use this second protocol for both the uplink and downlinksignals to facilitate the transmission of data at high speed from aremote site. This type of terminal can play the role of the hub in termsof transmitting directly on the downlink to “residential” terminals ineither a local spot beam mode or a broadcast mode to all spots beamssimultaneously.

[0020] The invention may also include “intra-Beam” and “inter-Beam”services, in which the capacity of the system is optimized by acoordinated network operation control center (“NOCC”). The NOCC canassign uplink frequencies and polarizations to individual groundterminals based on the signal destination, for both intra-beam andinter-beam transmissions. The NOCC may also assign a frequency bandwidthcompatible with a narrow-band uplink (the residential service) or awide-band uplink (the commercial service). Protocols for the residentialand commercial match the two protocols used by the hub. A portion of theuplink band is assigned to each service. The NOCC may also allocate afrequency band and polarization to designate the type of service basedon whether the communications link is inter-beam or intra-beam.

[0021] The invention may also include a router for directing the signalto the appropriate spot beams for inter-beam transmission. The routermay operate in one of two modes. First, the router may direct the signalto the appropriate spot beam by selection of the frequency used for theuplink. Alternatively, the router may also direct the signal to theappropriate spot beam based on the signal polarization. Additionally,the router may also be used with the broadcast mode. For the broadcastmode, the selection of a particular frequency sub-band and/orpolarization routes the uplink signal to into every downlink beam.Alternatively, the sub-band and/or polarization may be routed to theNOCC for a “double-hop” rebroadcast to all downlink beams.

[0022] The invention may further provide for power control in eachdownlink spot beam to optimize system capacity and throughput.Additionally, due to the individual spot beams being small and coveringa localized area, the local weather conditions and geographical locationcan be factored into to the power control for each beam. Additionally,by utilizing power control, channel allocation can be optimized to allowgreater numbers of channels in spot beams that encompass heavypopulation centers and fewer channels in spot beams covering lessdensely populated areas.

[0023] The invention may also provide a high-speed wide area network toconnect each hub in each spot to every other hub. The high-speed WAN maybe high-speed optical fiber, conventional landline connections,satellite links, or the like.

[0024] That the invention improves over the drawbacks of prior SATCOMsystem employing multiple spot beams and accomplishes the advantagesdescribed above will become apparent from the following detaileddescription of the exemplary embodiments and the appended drawings andclaims.

BRIEF DESCRIPTION OF DRAWINGS

[0025]FIG. 1 is an illustration of a prior art “bent-pipe” mode SATCOMconfiguration.

[0026]FIG. 2 is an illustration of a prior art “broadcast” mode SATCOMconfiguration.

[0027]FIG. 3 is an illustration of a prior art SES ARCS SATCOMconfiguration.

[0028]FIG. 4 is an illustration of a SATCOM system providing multiplespot beams to provide coverage of at least selected areas of the CONUSin accordance with an exemplary embodiment of the present invention.

[0029]FIG. 5 is an illustration of a representative spot beam coveragepattern of the CONUS in accordance with an exemplary embodiment of thepresent invention.

[0030]FIG. 6 is an illustration of an alternative spot beam coveragepattern of the CONUS in accordance with an exemplary embodiment of thepresent invention.

[0031]FIG. 7 is an illustration of an exemplary embodiment operating inan intra-spot beam mode.

[0032]FIG. 8 is an illustration of an exemplary embodiment operating inthe inter-spot beam mode.

[0033]FIG. 9 is an illustration of an exemplary embodiment operating inthe broadcast mode.

[0034]FIG. 10 is an illustration of an exemplary embodiment operating inthe remote hub broadcast mode.

[0035]FIG. 11 is an illustration of the frequency allocation of theuplink signal and the downlink signal for inter-spot beam mode based onsignal frequency for an exemplary embodiment of the present invention.

[0036]FIG. 12 is an illustration of a frequency-based router circuitused for the inter-spot beam mode in accordance with an exemplaryembodiment of the present invention.

[0037]FIG. 13 is an illustration of the frequency allocation of theuplink signal and the downlink signal for inter-spot beam mode based onsignal polarization in accordance with an exemplary embodiment of thepresent invention.

[0038]FIG. 14 is an illustration of a polarization-based router circuitused for inter-spot beam mode in accordance with an exemplary embodimentof the present invention.

[0039]FIG. 15 is an illustration of the frequency allocation of theuplink signal and the downlink signal for an inter-spot beam mode basedon both frequency and polarization of the signals in accordance with anexemplary embodiment of the present invention.

[0040]FIG. 16 is an illustration of a combinationfrequency/polarization-based router circuit used for inter-spot beammode in accordance with an exemplary embodiment of the presentinvention.

[0041]FIG. 17 is an illustration of a parent-dependent SATCOM inter-beamconfiguration in accordance with an exemplary embodiment of the presentinvention.

[0042]FIG. 18 is an illustration of an exemplary spot beam patternnetwork for a parent-dependent configuration for the Western UnitedStates.

[0043]FIG. 19 is an illustration of an exemplary embodiment of theinvention operating in a Network Operating Control Center (NOCC) SATCOMconfiguration.

[0044]FIG. 20 is an illustration of a combination frequency-based routercircuit used for the NOCC configuration in accordance with an exemplaryembodiment of the present invention.

[0045]FIG. 21 is an illustration of a 4:1, 3:1, and 2:1 combinercircuits used for on-board satellite transmitter power control inaccordance with an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0046] The current invention can provide a hub in every spot beam of asatellite for maximum frequency re-use and allows all signal processingto be accomplished on the ground. The notion of a hub in every spot beamis also fundamental to the notion of a high capacity, localbroadcast/data service through a digital video broadcast (DVB) downlinkformat. Otherwise the satellite downlink cannot access sufficient uplinkinformation bandwidth to broadcast into the multiple spot beams withunique data. Even though a direct broadcast satellite can broadcast tomillions of users, the capacity for information content is only about500 Mbps×2 (assuming 500 MHz bandwidth×2 polarizations), or 1 Gbps forthe whole coverage area. The current inventive concept envisions systemswith approximately 100 spot beams, each of which has ˜750 MHz bandwidthfor each of two polarizations, or 150 Gbps potential capacity.

[0047] The hub in every spot beam concept also allows the modulationformats between ground terminal uplink and downlink signals to bedifferent (i.e., FDMA on the uplink and TDMA on the downlink) whichpreviously' has been accomplished only by providing on-board digitalprocessing. However, placing a hub in every spot beam allows thesatellite to operate in a simple “bent-pipe design” with no on-boardprocessing.

[0048] The use of spatially isolated spot beams allows maximum frequencyre-use, which provides increased data capacity relative to thecontiguous beam approach in which the beam overlap requires a frequencyassignment approach and adjacent beams use only a portion of the band (4and 7 sub-band assignments are common). The isolated spot beam approachalso allows separate power control of each downlink beam to accommodatedifferent traffic patterns and satellite power limitations. This canalso be accomplished with a TDMA switching approach between downlinkbeams but at the expense of increased satellite and ground terminalcomplexity.

[0049]FIG. 4 illustrates an exemplary SATCOM system using a network ofspot beams to provide coverage of at least selected areas of the CONUS.A satellite 410, or a series of such satellites, stationed in ageosynchronous earth orbit above CONUS, provides the network of spotbeams 415. The SATCOM system may operate at either Ku-band frequencies,Ka-band frequencies, or both to provide broadcast video, local areabroadcast video and bandwidth-on-demand Internet access. The exemplarySATCOM system may use GEO satellites that produce narrow spot beams forboth the uplink and downlink signals so that a high data rate can beobtained on the uplink and downlink with a small dish size. For example,the effective radiated power (“ERP”) requirement for the uplink transmitantenna is typically {fraction (1/100)} of a Ku-band SATCOM systemscurrently in use and {fraction (1/10)} of announced Ka-band systems.

[0050]FIG. 5 illustrates a spot-beam coverage pattern of CONUS used byan exemplary embodiment of the present invention. The coverage patterntypically comprises a network of equally sized spot-beams coveringselected areas of the CONUS. Typically, each spot beam may have adiameter between seventy (70) and one hundred (100) miles. The spotbeams can be equally spaced to provide a substantially uniform coverageof the CONUS. In the alternative, the spot beams can be focused onselected areas of the CONUS.

[0051]FIG. 6 illustrates an alternative spot beam coverage pattern forCONUS using an exemplary embodiment of the invention. In this pattern, anetwork of equally sized, equally spaced spot beams are arranged toprovide coverage for areas having a high demand for services.Additionally, in areas where demand may be low, such as the northernplains states, a single, larger spot beam may be used to providecoverage. As the demand for services grows in the less populated areas,additional spot beams may be added to provide to meet the demand.

[0052] Additionally, the spot beams may be arranged in an unevendistribution to provide greater coverage in heavily populated areas andprovide less coverage in less densely populated areas. Furthermore,spacing of individual spot beams may be dynamically altered to providegreater additional coverage in a high growth area to meet the demand.For example, the eastern and western seaboards of the United States eachhave a greater population than the northern plains states. Therefore,the density of spot beams along the East and West coasts may be higherthan the density of spot beams over the northern plains states.Additional spot beams can be added to provide additional coverage as thedemand for SATCOM services increases.

[0053] One application of the hub service supported by the presentinvention is Internet Access for both data and multi-cast broadcasting.A protocol similar to the DVB format allows the system to provideselected types of data interchangeably. Another type of servicesupported by the use of a hub in each spot beam is regional datamulti-casting/broadcasting, in which all local TV stations are broadcastwithin a region. Yet another service could be national datamulti-casting/broadcasting, in which the data broadcast is the same inevery spot beam. This could implement the broadcast of nationallytelevised programming, or nationally broadcast data-casting.

[0054]FIGS. 7, 8, 9, 10 and 17 are illustrations of exemplaryembodiments of the invention. FIG. 7 illustrates a multi-beam SATCOMsystem 20 with a hub 706 in every beam 702 operating in an intra-spotbeam mode. In the SATCOM system 20, each spot beam 702 is spatiallyisolated from every other spot beam. This allows the SATCOM system 20 toachieve maximum frequency re-use. In contrast, for SATCOM systems inwhich the spot beams are contiguous, or overlap, signals from adjacentspot beams cause interference.

[0055] To overcome the interference from adjacent spot-beams, the SATCOMsystem 20 uses a frequency assignment, in which the frequency bands usedfor the uplink and downlink signals 710 are divided into severalsub-bands, typically between four (4) and seven (7) sub-bands. Forexample, if a SATCOM system uses four contiguous spot beams to coverCONUS, the uplink and downlink frequency bands would be divided intofour sub-bands. Each spot beam would be assigned a separate sub-band foruse on the uplink and downlink signal. Although using a frequencyassignment limits the interference between adjacent spot beams, theeffective bandwidth available is reduced by one quarter. By spatiallyisolating each spot beam from every other spot beam according to anembodiment of the invention, there is no interference. Therefore,sub-bands are not necessary and the entire frequency band is availablefor use in every spot beam. Spatially isolating the spot beams increasesthe bandwidth available for signal transmission by a factor of four.

[0056] In the case of intra-beam configuration, the ground terminals 704and hub 706 are located within the same beam. The intra-beamconfiguration operates in a similar manner to the “hub” configurationdiscussed above. A single ground terminal 704 transmits a signal on theuplink frequency to the satellite 708, which retransmits the signal onthe downlink frequency to another ground terminal 704. The satellite 708then transmits the signal on the downlink frequency to the appropriateground terminal 704.

[0057] If a ground terminal 704 in a first spot beam wishes tocommunicate with a ground terminal 704 in a second spot beam, the firstground terminal transmits a signal 710 on the uplink frequency to thesatellite 708, which retransmits the signal 712 on the downlinkfrequency to the hub 706 within the same spot beam. The signal is thenrouted over a land-based, high-speed wide-area network (WAN) 714 to thehub 706 in the same spot beam as the second ground terminal. The hub 706transmits the signal on the uplink frequency to the satellite 708 forretransmission to the second ground terminal over the downlinkfrequency.

[0058] In a similar manner, a one-way broadcast signal may betransmitted to every spot beam. The one-way broadcast may originate froma ground terminal located in a single spot beam. The broadcast signal istransmitted to the GEO satellite, which retransmits the broadcast to thehub located in the same spot beam. The signal may originate from the hubor from a source outside the network through the WAN. The hub thentransmits the broadcast signal to the GEO satellite, which retransmitsthe signal to every ground terminal in the spot beam.

[0059]FIG. 8 is an illustration of an exemplary embodiment operating inthe inter-spot beam configuration. In this configuration, each hub 806in a spot beam 802 communicates with another hub in another spot beamthrough the GEO satellite 808 in a hub-to-hub link 814. This allowsindividual terminals 804 in a first spot beam to communicate withindividual terminals 804 in a second spot beam. First, a ground terminal804 in a first spot beam transmits a signal to the GEO satellite 808,which retransmits the signal to the hub 806 located in the first spotbeam. The hub 806 determines the appropriate hub to which to route thesignal. Once the signal processing is complete and the signal routed tothe appropriate hub via the network link numbered 816, the signal istransmitted by the hub 806 in the first spot beam to the GEO satellite808, which retransmits the signal to the hub 806 in the second spotbeam. Finally, the hub numbered 806 in the second spot beam transmitsthe signal to the appropriate ground terminal 804 in the second spotbeam, or to the GEO satellite. 808.

[0060]FIG. 9 is an illustration of an exemplary embodiment operating inan inter-beam broadcast configuration. A hub 906 in a first spot beamtransmits a broadcast signal 910 on the uplink frequency to the GEOsatellite 908. The GEO satellite 908 receives the broadcast signal 910,shifts the signal frequency, to the downlink frequency and re-transmitsa signal 912 to each spot beam 902. The broadcast signal 910 mayoriginate from either an individual land-based terminal 904 or from thehub 906 located in the spot beam. The hub 906 in each spot beam 902 cancommunicate with the remaining hub via a network link 914.

[0061] The broadcast signal 910 may be transmitted in one of two ways.First, the signal may be a local broadcast signal intended only forreception by ground terminal within the spot beam where the signaloriginated. For example, in the greater Atlanta area, a local broadcast,such as a local news broadcast, is typically intended to be seen only byviewers within the greater Atlanta area. Each news agency may transmittheir broadcast signal directly from a ground terminal or may route thesignal through a local hub centrally located within the spot beam. Thelocal news broadcast signal is transmitted to the GEO satellite, whichre-transmits the signal to viewers residing in the greater Atlanta area.

[0062] Secondly, the broadcast signal may be a locally generated signalwithin an individual spot beam intended for national broadcast. Underthis scenario, an individual ground terminal or a local hub locatedwithin a first spot beam transmits a broadcast signal to the GEOsatellite on the uplink frequency. The GEO satellite then broadcasts thesignal into every spot beam where it is received by the individualground terminals. An example of this mode of broadcast signal would be anational news service, such as Cable News Network (CNN), which islocated in Atlanta, Ga. The CNN broadcast signal, which originates inAtlanta, is transmitted from an individual ground terminal in the spotbeam providing coverage to the greater Atlanta area to the GEOsatellite. The GEO satellite then re-broadcasts the signal not only toeach ground terminal in the same spot beam, but to each ground terminalin every spot beam.

[0063]FIG. 10 is an illustration of an exemplary embodiment operating ina remote-hub broadcast configuration. Again, the SATCOM system comprisesa series of spot beams 1002 originating from the satellite 1008 andilluminating the earth surface. At least one spot beam 1002 encompassesonly a single, remote hub 1005. Each of the remaining spot beams 1002encompass a number of ground terminals 1006 and a single hub 1004.Typically, the spot beam that encompasses the remote hub is the samesize as the other spot beams in the network. However, the remote hub maybe located in a remote portion of the CONUS, where the demand forsatellite service is low, such as in the Northern Plains States. In thiscase, the spot beam covering the remote hub may be considerably largeror smaller than the remaining spot beams.

[0064] The remote hub 1005 may receive a national broadcast signal 1012,which originates from any specified source. The signal is fed to theremote hub 1005 through a WAN 1014 for transmission to the GEO satellite1008. For example, the broadcast signal 1012 may be a national broadcastsignal that is intended to be transmitted to every ground terminal inthe CONUS. For example, a national news agency, such as the NationalBroadcasting Company (NBC) may transmit its broadcast signal 1010 fromthe remote hub to the GEO satellite for transmission back to everyground terminal. Alternatively, every hub 1004 may be connected to theremote hub 1005 through the WAN 1014. Each hub 1004 could then send thelocal broadcast signal to the remote hub 1005 via the WAN 1014 fortransmission on the national broadcast signal, whenever local eventswarranted broadcasting news on a national scale.

[0065]FIG. 11 is an illustration of the frequency allocation of theuplink signal and the downlink signal for inter-spot beam configurationbased on signal frequency in accordance with an exemplary embodiment ofthe present invention. Specifically, FIG. 11 illustrates an exemplaryfrequency allocation for the Ka-band frequencies 1102, which typicallyrange between 18.3 GHz and 30.0 GHz. The Ka-band frequency typically hasan uplink frequency band 1104 ranging from about 28.35 GHz to about 30.0GHz and a downlink frequency band 1106 ranging from about 18.3 GHz toabout 20.2 GHz. The uplink and downlink frequency bands may further bedivided into sub-bands. The first sub-band 1108 may be used for thebroadcast transmission and is typically 750 MHz wide to support hubswhich provides a nearly symmetrical data rate over a 36 MHz bandwidth.It will be appreciated that the frequency allocation defined in FIG. 11represents only one of many possible different allocations of thefrequency spectrum to support the exemplary satellite communicationsystem.

[0066] The second sub-band 1110 may be used for a SATCOM return channelfrom individual terminals. The second sub-band is typically 250 MHz wideand supports 250 individual ground terminals each with a 1 MHzbandwidth. The use of the two separate bandwidths in the two sub-bandsallows the SATCOM system to have an asymmetrical data rate that ischaracteristic of most Internet access, i.e., a low-speed uplink datarate and a high-speed downlink data rate to minimize transmitter powerand dish size for the ground terminal.

[0067] The SATCOM ground terminal typically provides high gain uplinkspot beams, thereby minimizing the need for ground terminal with a higheffective radiated power (ERP). Additionally the SATCOM ground terminalmay provide a high power SATCOM transmitter into the narrow downlinkspot beam, which minimizes the size of the receiving aperture on theground. Typical uplink data rates are envisioned in the 1-2 million bitsper second (Mbps), while the downlink will provide peak rates of 20-40Mbps. The uplink air interface typically will be frequency divisionmultiple access (FDMA) with time division multiple access (TDMA)overlaid to further accommodate lower data rates. For example, thedownlink air interface may be DVB-S, a well-accepted protocol which canaccommodate a combination of MPEG-2 video and data. The important pointis that the hub service allows for different air interfaces on theuplink/downlink without on-board processing on the satellite.

[0068] For intra-beam services, a portion of the second uplink band usedby the ground terminals is allocated to the “intra-beam” service anddepicted as Δf_(2A). This portion of the band is then filtered at theinput of each receive spot beam. The designation of an “inter-beam”signal may also be accomplished by restricting part of the band to the“inter-beam segment, shown as Δf_(2B).

[0069] Because the frequency of each ground terminal and hub areassigned and coordinated within the system, not only the groundterminals but also the hub can provide “intra-beam” and “inter-beam”communications. This allows the introduction of a new concept of ahigh-speed ground terminal that uses the same uplink format as the hub.This terminal will be referred to as a “commercial” terminal, or as a“remote hub.” These terminals can transmit into the “intra-beam”service, or into the “inter-beam” or broadcast service, in the same wayas the ground terminals using a different part of the uplink band with adifferent air interface. For example, a “remote hub” in one spot beam isassigned a frequency or polarization that is allocated to “broadcast”,and that channel is broadcast into all downlink beams.

[0070]FIG. 12 is an illustration of an exemplary frequency-based routercircuit used for the inter-spot beam configuration. The frequency-basedrouter circuit consists of n identical circuits connected to a singlerouter 1222, where n is the number of spot beams used by the SATCOMsystem. An uplink signal, comprising both the first and secondsub-bands, enters the router through one of the antennas 1202 and isthen amplified by a linear LNA 1204. The signal then passes through ademultiplexer 1206, or “demux,” which separates the signal into twosignals. The first signal is used for intra-beam routing and consists ofthe broadcast signal in the first sub-band Δf₁, and the intra-beamsegment Δf_(2A) signal. The intra-beam signal then passes though adownconverter 1208, which shifts the frequency to the downlinkfrequency. Next, the intra-beam signal passes through a power adjustcircuit 1210, in which the output transmission power is set. Next, theintra-beam signal is filtered in a filter 1212 to remove unwanted noisefrom the signal. Finally, the signal passes through an amplifier 1214before it is transmitted via antenna 1216 on the downlink to the groundterminals located within the same spot beam.

[0071] The second signal is used for inter-beam routing, which consistsof the inter-beam portion, Δf_(2B) of the second sub-band. Theinter-beam portion, Δf_(2B) of the second sub-band is further separatedinto n equal segments, where n is the number of spot beams employed bythe SATCOM system. Each segment directly corresponds to an individualspot beam (i.e., the first segment corresponds to the first spot beam,the second segment corresponds to the second spot beam, etc.). Thefrequency of the inter-beam signal is shifted to the downlink frequencyby passing the signal through a second downconverter 1218. The signalthen passes through a filter 1220 to remove unwanted noise beforepassing through a router 1222. The router 1222 then redirects the signalto the appropriate antenna 1216, depending on which segment of theinter-beam frequency, Δf_(2B) was used to transmit the signal. Forexample, if the signal is placed in the first segment of the sub-band,the router will redirect the signal to the antenna corresponding to thefirst spot beam, and so on. The inter-beam signal is filtered by thefilter numbered 1212 and amplified by the amplifier 1214 before beingtransmitted through the appropriate spot beam to the secondground-terminal.

[0072]FIG. 13 is an illustration of the frequency allocation of theuplink signal and the downlink signal in the Ka-band frequency for usewith polarization-based routing in the inter-spot beam mode inaccordance with an exemplary embodiment of the present invention. Thefrequency allocation 1302 for the Ka-band typically range between 18.3GHz and 30.0 GHz. The Ka-band frequency typically has an uplinkfrequency band 1304 ranging from about 28.35 GHz to about 30.0 GHz and adownlink frequency band 1306 ranging from about 18.3 GHz to about 20.2GHz. However, there are two identical channels for the uplink and thedownlink frequencies: one for a right circularly polarized (RCP) signaland a second channel for a left circularly polarized (LCP) signal.

[0073] The uplink and downlink frequency bands may be further dividedinto sub-bands. The first sub-band 1308 may be used for broadcasttransmission and is typically 750 MHz wide. The second sub-band 1310 maybe used for a SATCOM return channel from individual hubs and istypically 250 MHz wide.

[0074] Each SATCOM ground terminals would employ a dual polarized uplinkantenna with a switchable transmitter that could excite eitherpolarization. For one polarization, such as RCP, the received signal onthe satellite would go through the normal bent pipe processing into thesame downlink spot beam. For the other uplink polarization, such as LCP,the received signal would be channeled through the on-board apolarization-based router to each of the other spot beams. Those skilledin the art will appreciate that the frequency allocation defined in FIG.13 represents only one of many possible different allocations of thefrequency spectrum to support the exemplary satellite communicationsystem.

[0075]FIG. 14 is an illustration of an exemplary polarization-basedrouter circuit used for inter-spot beam mode. The uplink signal,containing both RCP and LCP signals, is passed by an antenna 1402 andsplit into two separate signals by an orthogonal mode transducer (OMT)1404. The LCP signal, which is used for inter-beam communications, isdirected to a router 1400 for transmission to the appropriate spot beam.The LCP signal is amplified and filtered before entering the router1400, where, in turn, the signal is directed to the appropriate spotbeam.

[0076] The RCP signal, which is used for intra-beam communications andcontains both the broadcast signal and the ground terminal returnsignal, passes through an amplifier 1406 before being separated by ademultiplexer 1407. After the two signals are separated, downconverters1408, 1418 shift each signal to the downlink frequency. The signals thenpass through power adjust circuits 1410, 1420 to adjust the amplitude ofthe signals. Next, the signals are combined and passed through a filter1412 before being amplified by a high power amplifier 1414. The RCPsignal then passes through another orthogonal mode transducer 1404 whereit is combined with an LCP signal intended for inter-beamcommunications. The combined signal is transmitted by an antenna 1416.

[0077]FIG. 15 is an illustration of the frequency allocation of theKa-band signal for an inter-spot beam router configuration based on bothfrequency and polarization of the signal in accordance with an exemplaryembodiment of the present invention. The Ka-band 1502 is divided into anuplink band 1504 with a frequency of Δf_(uplink), and a downlink band1506 with a frequency of Δf_(downlink). Each uplink band and downlinkband has two signals, one signal having a left hand circularpolarization and the other signal having a right hand circularpolarization. The uplink and downlink frequency bands may be furtherdivided into sub-bands. A first sub-band 1508 may be used for broadcasttransmission and is typically 750 MHz wide. A second sub-band 1510 maybe used for a SATCOM return channel and is typically 250 MHz wide. Itwill be appreciated that the frequency allocation illustrated in FIG. 15represents only one of many possible different allocations of thefrequency spectrum to support the exemplary satellite communicationsystem.

[0078]FIG. 16 is an illustration of a combinationfrequency/polarization-based router circuit used for inter-spot beammode communications on board a satellite in accordance with an exemplaryembodiment of the present invention. Specifically, FIG. 16 illustratesan exemplary circuit used for routing of the user uplink based onpolarization and frequency of the MF/TDMA return channel. The satelliteground terminal would employ a dual polarized uplink antenna with aswitchable transmitter that could excite either polarization. For theLCP uplink polarization, the received signal would be channeled throughthe on-board router to other spot beams. For the RCP, the receivedsignal is separated into 2 sub-bands by a demultiplexer. One sub-band isdownconverted and routed to the appropriate beam by the frequencyrouter. The other sub-band would go through the normal bent pipeprocessing into the same downlink spot beam.

[0079] Referring still to FIG. 16, the uplink signal, containing bothRCP and LCP signals, is passed by an antenna 1602 and split into twoseparate signals by an orthogonal mode transducer (OMT) 1604. The LCPsignal, which is typically used for inter-beam communications, isdirected to a router 1600 for transmission to the appropriate spot beam.The LCP signal is amplified and filtered before entering the router1600, where, in turn, the signal is directed to the appropriate spotbeam.

[0080] The RCP signal, which is typically used for intra-beamcommunications and contains both the broadcast signal and the groundterminal return signal, passes through an amplifier 1606 before beingseparated by a demultiplexer 1607. After the two signals are separated,down coverters 1608, 1618 shift each signal to the downlink frequency.The signals then pass through power adjust circuits 1610, 1620 to adjustthe amplitude of the signals. Next, the signals are combined and passedthrough a filter 1612 before being amplified by a high power amplifier1614. The RCP signal then passes through another orthogonal modetransducer (OMT) 1604, where it is combined with an LCP signal intendedfor inter-beam communications. The combined signal is transmitted by anantenna 1616.

[0081]FIG. 17 illustrates a parent-dependent configuration for theinter-beam mode, in which a hub 1704 is installed in the parent beam1702 but not in the dependent beams 1718, in accordance with anexemplary embodiment of the present invention. If a hub is not installedin a spot beam, the exemplary embodiment allows for an inter-beam accessfrom a ground terminal 1706 to a hub in another spot beam. This allowsthe ground terminal to access downlinks for the inter-beam broadcastservice, but not the “local channel” delivery service. Theparent-dependent configuration may be used for highly populated areasthat are surrounded by sparsely populated areas. For example, the parentbeam can be directed to cover Los Angeles, while the dependent beams cancover Northeastern California and Central Nevada, as shown in FIG. 17.

[0082] The parent beam 1702 provides coverage for the highly populatedarea while one or more dependent beams 1718 provide coverage for thesparsely populated areas. Each parent spot beam has a hub numbered 1704centrally located within the footprint of the spot beam and a number ofindividual ground terminals 1706. For intra-beam communications betweenthe ground terminals 1706 and the hub 1704 or between two groundterminals 1706, the ground terminals transmit an uplink signal 1714having one type of polarization, such as left circular polarization tothe GEO satellite 1708 equipped with a polarization-based routercircuit. The router would then route the left circularly polarizedsignal as a downlink signal 1716 back to the parent spot beam.

[0083] For broadcast transmissions, the hub 1704 in the parent spot beam1702 transmits two broadcast signals 1710, one right circularlypolarized and one left circularly polarized, simultaneously to the GEOsatellite. A polarization-based router in the GEO satellite separatesthe two signals and transmits the left circularly polarized signal 1716back to the parent spot beam and the right circularly polarized signals1722 down to the dependent spot beams.

[0084] Additionally, frequency routing may be added to the polarizationrouting to provide added flexibility in determining which programs aretransmitted to which dependent beams. For example, a right circularlypolarized frequency band used for broadcast data may be divided into nequal segments, where n is the number of spot beams employed by theSATCOM system. Each segment directly corresponds to an individualdependent spot beam (i.e., the first segment corresponds to a firstdependent spot beam, the second segment corresponds to a seconddependent spot beam, etc.). Separate, independent broadcast signalscould then be assigned to the separate segments to provide localizedbroadcast data to these areas covered by the dependent spot beams.

[0085]FIG. 18 illustrates a spot beam distribution for aparent-dependent inter-beam service in accordance with an exemplaryembodiment of the present invention. Parent spot beams 1802 may providecoverage to highly populated area such as the region stretching from SanFrancisco, Calif. to San Diego, Calif. In each of these parent spotbeams, both local and broadcast services may be provided. However, inareas such as central Nevada, and northern California, where thepopulation and demand for services is small, dependent spot beams 1804may be used to receive broadcast services from the parent beams.

[0086]FIG. 19 illustrates an alternative method for broadcast servicerouting. A Network Operating Control Center (NOCC) 1916 operates in aNOCC spot beam 1910, which is created in an area separated from all theother service spot beams numbered 1902 in accordance with an exemplaryembodiment of the present invention. A portion of the uplink band is setaside for broadcast user return signals. These signals, once received bythe input spot beam antennas and amplified, are combined in thefrequency domain with a power combiner. The Network Operating ControlCenter 1916 coordinates uplink frequencies so that no two broadcastsignals use the same frequency band. The combined signal is routed forbroadcast by the satellite numbered 1908 to the ground terminals 1904 inthe downlink spot beams 1902 via a retransmission 1912 from the NetworkOperating Control Center 1916. This service is a “double-hop” servicebecause of the intermediate transmission to the network control center.Alternatively, the signals intended for broadcast from the NetworkOperations Control Center 1916 could be delivered through the WAN 1914from a hub 1906 or user of the satellite network or directly from anoutside source.

[0087]FIG. 20 illustrates the use of frequency-based routing toaccommodate a NOCC within the network of spot beams in accordance withan exemplary embodiment of the present invention. The frequency-basedrouter circuit comprises n identical circuits connected to a signalrouter 2022 or to a high power amplifier 2014, where n is the number ofspot beams used by the SATCOM system. In contrast to the frequency-basedrouter circuit shown in FIG. 12, a network operating control centerprovides an input to the router circuit.

[0088] A numbered uplink signal can enter the router circuit through oneof the antennas numbered 2002 and is then amplified by a linear LNA2004. The signal then passes through a demultiplexer 2006, or “demux,”which separates the signal into two signals. The first signal passesthrough a down converter numbered 2008, which shifts the frequency tothe numbered downlink frequency. In turn, this downconverted signalpasses through a numbered power adjust circuit 2010, in which the outputtransmission power is set. The output of the power adjust circuit 2010is passed to the filter 2012 to remove unwanted noise prior toincreasing the amplitude of the signal at the amplifier numbered 2014.The output of the amplifier 2014 is transmitted by the antenna 2016.

[0089] The second signal output by the demultiplexer 2006 is passed to adown converter 2018, which shifts the frequency to the downlinkfrequency. In turn, the output of the down converter numbered 2018 isfiltered by a filter 2020 to remove unwanted noise. This process can becompleted numbered n times based upon the n number of spot beamsemployed by the SATCOM's system. Each output of filter 2020 is summed ata combiner and output to an amplifier 2014 for transmission via theantenna 2016.

[0090] The input signal provided by the Network Operating Control Centeris received by the antenna 2002′, amplified by the amplifier 2003,filtered by the filter 2005, and output to the router 2022. In turn, therouter 2022 can output a redirected signal to the appropriate antenna2016.

[0091]FIG. 21 illustrates an exemplary system for controlling thesatellite spot beam downlink transmitter power to adjust the channelcapacity by combining circuits. The spot beam network concept allowssome unique flexibilities on-board the satellite that a conventional DBSsatellite does not have. A standard architecture Ku-band DBS satellitemust provide full coverage of CONUS geography. Therefore, the DBSsatellite must transmit its downlink power at a more or less constantlevel across the area. This is particularly wasteful when transmissionof local channel DBS is only intended for a small area within CONUS.Additionally, spot beams over large population centers may require morecapacity than less populated areas. Also, the peak periods of use willvary slightly from East Coast to West Coast during the day leading tovariable power requirements. The variable power requirements may beaccommodated by adopting a total power management control concept on thesatellite in which downlink beams are excited by transmissions circuits,which combine 1, 2, or 4 high power sources. For example, consider anetwork of 100 spot beams in the CONUS geography. Each could transmit 15W on a continuous DVB downlink basis, totaling 1.5 KW of transmit power.Alternately, the top 10 population centers could be allocated 40 W, thenext 20 centers 20 W, and the remaining 70 centers only 10 W.

[0092] It should be understood that the foregoing pertains only toexemplary embodiments of the present invention, and that numerouschanges may be made to the embodiments described herein withoutdeparting from the spirit and scope of the invention.

What is claimed is:
 1. A satellite communications system for distributing information to user terminals located within a plurality of spot beams, the satellite communications system comprising: a communications satellite in a geosynchronous orbit; a plurality of hubs each located within a respective spot beam, and adapted to: route information received from a first user terminal located within a first spot beam via the communications satellite to a second user terminal located within a selected one of the spot beams via the communications satellite; wherein the communications satellite is adapted to: receive the information according to a first protocol from the first user terminal; transmit the information according to the first protocol to a first hub located within a selected one of the spot beams; receive the information according to a second protocol from the first hub; and transmit the information according to the second protocol to a second user terminal located within a selected one of the spot beams.
 2. The satellite communications system according to claim 1 wherein each of the spot beams is spatially isolated from the other spot beams.
 3. The satellite communications system according to claim 1 wherein the first hub is located within the first spot beam.
 4. The satellite communications system according to claim 1 wherein the first hub located within one of the spot beams other than the first spot beam.
 5. The satellite communications system according to claim 1 wherein the communications satellite is further adapted to: transmit the information to the second user terminal at a first frequency; and transmit the information at a second frequency to a third user terminal located within a selected one of the spot beams.
 6. The satellite communications system according to claim 1 wherein the communications satellite is further adapted to: transmit the information to the second user terminal at a first polarization; and transmit the information at a second polarization to a third user terminal located within a selected one of the spot beams.
 7. The satellite communications system according to claim 1 further comprising a network control center adapted to assign frequencies and polarizations for the information received from the first user terminal and for the information transmitted to the second user terminal.
 8. The satellite communications system according to claim 1 wherein the first protocol and the second protocol are the same protocol.
 9. The satellite communications system according to claim 1 wherein the communications satellite further comprises a router adapted to direct the information to user terminals located within a selected one of the spot beams by selecting the frequency or polarization of the information.
 10. The satellite communications system according to claim 1 wherein the communications satellite comprises a downlink transmitter power controller to adjust the power level at which the information is transmitted to the second user terminal.
 11. The satellite communications system according to claim 1 further comprising a wide area network interconnecting a selected subset of the hubs.
 12. A user terminal for communicating information with other user terminals through a satellite communications system, the satellite communications system including a communications satellite in geosynchronous orbit and a plurality of hubs, the communications satellite including an antenna, each hub located in one of a plurality of spot coverage areas formed by the antenna, the user terminal being adapted to: transmit information to one of the hubs via the communications satellite according to a first protocol; and receive information from the hub via the communications satellite according to a second protocol.
 13. The user terminal according to claim 12 wherein the user terminal is located in the spot coverage area in which the hub is located.
 14. The user terminal according to claim 12 wherein the user terminal is located in one of the spot coverage areas other than the one in which the hub is located.
 15. The user terminal according to claim 12 wherein the first protocol and the second protocol are the same protocol.
 16. A method for communicating between user terminals through hubs, the user terminals being located in spot coverage areas defined by a spot beam antenna on a geosynchronous communications satellite, each of the hubs located in a respective spot coverage area, the method comprising the steps of: transmitting a first signal from a first user terminal to a hub through the satellite according to a first protocol; and receiving a second signal at a second user terminal from the first hub through the satellite according to a second protocol.
 17. The user terminal communicating method according to claim 16 further comprising the steps of: at the hub, transmitting the second signal at a selected frequency and a selected polarization to the satellite; and at the satellite, routing the second signal to at least one of the spot coverage areas based on the frequency and polarization of the second signal.
 18. The user terminal communicating method according to claim 16 wherein the first signal transmitting step comprises transmitting the first signal from the first user terminal through the satellite to a first hub located in a different spot coverage area.
 19. The user terminal communicating method according to claim 16 further comprising the step of receiving the second signal at a third user terminal, wherein the second user terminal and the third user terminal are located in different spot coverage areas.
 20. The user terminal communicating method according to claim 16 further comprising the step of receiving the second signal at user terminals located within each of the spot coverage areas.
 21. The user terminal communicating method according to claim 16 further comprising the step of receiving the second signal at a third user terminal, wherein the first, second, and third user terminals are located in the same spot coverage area.
 22. The user terminal communicating method according to claim 16 further comprising the step of communicating between at least two of the hubs through a ground-based communications link.
 23. The user terminal communicating method according to claim 22 wherein the communicating step comprises communicating over a wide area network.
 24. The user terminal communicating method according to claim 16 further comprising the step of assigning, in a network operations control center, frequencies and polarizations to the hubs and user terminals.
 25. A frequency-based router circuit for use in a satellite communications system, the satellite communications system comprising a ground hub; a communications satellite; and a plurality of user terminals located in a plurality of spot coverage areas, the router circuit comprising: a first demultiplexer for separating an inter-beam signal from a plurality of intra-beam signals; a second demultiplexer for separating the intra-beam signals; and a router adapted to route each of the inter-beam signal and the intra-beam signals to respective spot beam antennas on the satellite.
 26. The frequency-based router circuit of claim 25 further comprising a plurality of downconverters for frequency converting respective inter-bean and intra-beam signals.
 27. The frequency-based router circuit of claim 25 further comprising a power adjust circuit for setting the output power level of a selected at least one of the inter-beam signal and the intra-beam signals. 